1. Field of the Invention
The present invention relates to a development device which develops an electrostatic image formed on an image bearing member using a developer and an image forming apparatus, such as a copying machine, a printer, and a facsimile, which is provided with the development device.
2. Description of the Related Art
Generally, a recording material is conveyed in a horizontal state in many components of an image forming apparatus which forms an image on the recording material such as plain paper and OHP film, using a developer. Therefore, the image forming apparatus has a disadvantage that the apparatus has a large installation area.
On the other hand, for example, Japanese Patent Application Laid-Open No. 6-202390 discloses an image forming apparatus, in which the apparatus is formed in a stand-up state in order to decrease the apparatus installation area and the recording material is conveyed while substantially being substantially upright.
Japanese Patent Application Laid-Open No. 8-314251 discloses a detailed configuration of a development device in the “stand-up type” image forming apparatus. As shown in FIG. 10, a case 100 is partitioned into a developer refilling chamber 102 and a development chamber 103 by a partition wall 101, a new developer is stored in the developer refilling chamber 102, and a development roller 104 is disposed in the vertical direction in the development chamber 103.
A cylindrical developer conveying path 105 is provided between the developer refilling chamber 102 and the development chamber 103, and a conveying screw 106 is rotatably disposed in the developer conveying path 105. Developer discharge ports 102a and 103a are formed in a bottom portion of the developer conveying path 105. Therefore, the developer from the development chamber 103 and the developer from the developer refilling chamber 102 flow into a bottom portion of the conveying screw 106. Accordingly, when the conveying screw 106 is rotated, the developer located in the bottom portion of the conveying screw 106 is conveyed to the upper portion and supplied from a supply port 107 into the development chamber 103.
Japanese Patent Application Laid-Open No. 4-358182 discloses a configuration in which a rotational axis of a development sleeve is provided so as to be orientated toward the vertical direction. A belt is disposed in order to supply a magnetic developer from a lower portion to an upper portion along a surface of the development sleeve. A plurality of blades are provided at equal intervals on a surface of the belt, and the magnetic developer is conveyed by the blades.
The stand-up type image forming apparatus has an advantage in that the installation space can be decreased.
However, the above-described conventional configurations have the following problems. That is, in the configuration in which the toner is supplied to the development sleeve while the developer located in the bottom portion is conveyed to the upper portion by the toner conveying unit, the supplied toner amount is decreased as the toner conveys up, which causes a problem in an uneven coating is generated in the vertical direction of the development sleeve.
Fluidity of the developer is easily changed by a change in humidity or temperature in an environment in which the toner is used, and sometimes an amount of developer supplied to the developer bearing member becomes unstable. In the case where the developer is conveyed in the gravity direction, a difference in the amount of supplied developer is easily generated in the vertical direction of the developer bearing member. That is, sometimes uniform image formation is hardly performed depending on the environment in the conventional method in which the developer is conveyed to the upper portion by the developer conveying member and the developer flowing down near the developer bearing member.